1. Field of the Invention
The present invention relates to a device for measuring a speed of movement of an object, and in particular, to a device for measuring a speed of a moving object, for example, a tennis ball which moves a predetermined distance between a starting point and a landing point.
2. Description of the Prior Art
A movement speed measuring device of a moving object is known in the art in which, for example, an electromagnetic wave such as a laser beam, or an ultrasonic wave of a predetermined frequency is transmitted against the moving object, and the frequency of a reflected wave reflected from the moving object is measured to determine a speed of movement of the object by utilizing the Doppler effect.
However, in this prior art movement speed measuring device, an instantaneous speed of the moving object can be measured accurately. On the other hand, the drawbacks are involved in that since the electromagnetic wave or ultrasonic wave of a predetermined frequency has to be transmitted against the moving object, another person is required to perform the transmission operation. Thus, for example, in the practice of serving in tennis, in order that the server himself knows a speed of the tennis ball served by him, it is necessary to ask another person for help. Consequently, it is inconvenient, and further, the movement speed measuring device per se becomes large in size and expensive.